The instant invention relates to knitting methods and more particularly to a method of producing a fiber string having a plurality of flexible loops or tufts extending outwardly therefrom.
Fiber strings comprising a central rope-like backbone and having a plurality of flexible loops or tufts extending outwardly therefrom have heretofore been used as contact elements in waste water treatment apparatus. For example, a fiber string of this type is illustrated and described in U.S. Pat. No. 4,422,930. In the '930 patent, the fiber string is suspended on a frame system for presentation to an effluent flow.
Although the presently available contact elements are effective, there is one major drawback: the contact elements are very expensive to produce. While the contact elements do not need to be repeatedly replaced, a significant amount of the fiber string material is nevertheless required in maintaining such a treatment system.
Accordingly, among the several objects of the instant invention is the provision of a method for inexpensively producing a contact element using conventional knitting apparatus.
The instant invention provides a novel method of producing a fiber string contact element comprising the steps knitting a loop pile fabric with non-soluble and soluble yarns, and then dissolving the soluble yarns in a solution to release the knitted loops. More specifically, the loop pile fabric is formed with a central rib, or backbone, knitted from a plurality of non-soluble yarns, a plurality of loops knitted into the central rib such that terminal ends thereof extend outwardly from opposite sides of the central rib, and a retaining rib respectively knitted into the terminal ends of the loops on each side of said central rib. The loops are knitted from a plurality of non-soluble yarns, and the retaining ribs are knitted from a plurality of soluble yarns. The retaining ribs hold the ends of the loops during knitting. However, the ends of the loops are subsequently freed from the retaining ribs after knitting by immersing the entire fabric in a solution capable of dissolving the soluble yarns, i.e. the retaining ribs. The resulting product is a fiber string comprising a strong rope-like backbone having a plurality of yarn loops extending outwardly therefrom.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.